HeNe Laser Transmitter/Receiver - This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself. LASERs are available from MWK industries. __ Designed by Aaron Cake

HF TRANSCEIVER - This page will describe the construction of a multI band SSB transceiver. Because I do 99% of my operating on my four favourite bands, I decided to build a four band rig with provision for adding a fifth band later. The design can be used on any band from 160M to 10M. Mine covers 80M, 40M, 17M, 10M. __ Designed by EI9GQ homebrew radio

Isolated MOSFET driver has wide duty-cycle range - 29-Apr-04 EDN Design Ideas: The main application for the circuit in Figure 1 is for driving power MOSFETs with signals ranging in frequency from 1 Hz to 300 kHz and with duty cycles from 0 to 100%. You achieve this goal by using a coreless pc-board transformer. The switching frequency in most power-electronics circuits ranges from a few hertz to a few hundred kilohertz __ Circuit Design by Jesus Doval-Gandoy and Moises Pereira Martinez, ETSI Industriales, Vigo, Spain

Laser transmitter/receiver - This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself. LASERs are available from MWK industries. __ Designed by Aaron Cake

Lego Mindstoms IR Link PIC transceiver - I just finished a half duplex serial asynchronous link from a simple PIC circuit to the RCX. it is able to receive codes from the RCX (or Lego RCX remote control) store them in RAM & EEPROM and transmit any IR op-code to the RCX in turn. included in the firmware is a routine that takes any opcode (s) and expand it to the proper IR packet for transmission to the RCX. I'veused the UiRT circuit with a few modifications for the hardware. The UiRT includes a serial port programmer for the PIC 16F84A so you won't need a separate programmer. Here's the website where you can find the programmer. Here are the modifications to get the UiRT to work with the RCX. __ Designed by Lloyd Gordon

Local Oscillator - The local oscillator is based on the Franklin oscillator, that was so popular in the first half of this century. The Franklin circuit used two vacuum tubes, this circuit uses two direct coupled FET's. The inductor L1 is wound on a ceramic former, about 1/2 inch (12.5mm) Dia. You can make a ceramic coil former from an old 1KW electric fire (heater) element. Nick the element with a hacksaw, and break it on a hard surface __ Designed by EI9GQ homebrew radio

Microphone Amplifier and LPF - The USB/LSB carrier oscillators are fairly conventional, common collector Colpitts oscillators. I used BC548 transistors, not because they are particularly well suited to the job, but because I had a few of them in my junk box. The crystal frequencies are chosen to match the SSB filter in your rig (7.7985/7.8015 MHz in my rig.) __ Designed by EI9GQ homebrew radio

Multi-Band HF Direct Conversion Transceiver - This project is a work in-progress. it was originally going to be only a single band transceiver, hence the single vco. But somewhere along the way I decided to make it multI band (80/40/20) and add a pll synthesizer __ Designed by John Price VK3AJG

Passive filters fill the bill at audio frequencies - 02/01/01 EDN Design Ideas: Low-frequency filters, particularly at audio frequencies, usually take the form of active filters. These filters eliminate expensive inductors with windings of many turns. Both analog and digital active filters are most compatible with large-scale integration at the subsystem and system levels. __ Circuit Design by Richard Kurzrok, Queens Village, NY

Post Mixer Amp - SSB Transceiver-Receiver Section: The post mixer amplifier, makes up for the losses in the passive mixer and i.F. port attenuator. The transistor is a 2N4427, if you don't have one, try a 2N3866, 2N5109, on any similar, medium power VHF transistor. The output transformer is 10 turns with a tap at 4 turns. The core is the same, high permeability ferrite ring, used in other parts of this project. The output supplies DC current for the RX/TX switching diodes at the SSB filter input __ Designed by EI9GQ homebrew radio

RS-232 Laser Transceiver - Laser based projects used to be expensive, until the development of solid state lasers. This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over 200 meters using a laser beam. A low cost transmitter only circuit is also presented here for use in one way communication and other laser based projects __ Designed by shaunwilson19 @ yahoo.com

Rx I.F. and Product Detector - SSB Transceiver-Receiver Section: Two silicon switching diodes are used for receive/transmit switching of the input side of the SSB filter. The iF amp is an MC1350P. This device can give more than 60dB of gain at 7.8Mhz. I decided to use a single iF amplifier stage, followed by a relatively high gain AF amp (60dB +). The output transformer is a KANK3334R, with a 100pf capacitor and 5K6 resistor across the primary. __ Designed by EI9GQ homebrew radio

Simple Circuit 40 meters CW QRP Transceiver - This project describes a little QRP transceiver “full legal power” (5 W at 12 V) for the 40 meters band. The RiG may be built in a gradual manner, in fact it is divided in two main modules, or you may also complete only the RX module __ Designed by Francesco Morgantini IK3OIL

SSB Tramsceiver, Exciter Board - Now that people are getting married, and having babies on the internet, isn't it about time someone designed and built an SSB rig on the net?. The rig will be built up from various modules, starting with the SSB exciter board. The first prototype board has been built and tested on the bench but not on air. The resulting SSB signal looks good on the scope, and sounds ok on a monitor receiver. __ Designed by EI9GQ homebrew radio

SSB Transceiver, Transmitter Section - For the transmit mixer, I used a simple single ended JFET mixer. The FET is a J113. The inductors are TOKO KANK3334. You can wind your own on TOKO, or similar formers PRI = 18T SEC = 3T. The transformer at the output of the first stage is 6 Turns, bifilar wound on a ferrite toroid, of the same type used for the RX mixer. I used 2N4427's for both stages. The 2N3866 or 2N5109 should also be suitable. Gain is about 30dB, more than enough to bring the 1mW, from the TX mixer, up to several hundred mW. Use a heat sink on both transistors. __ Designed by EI9GQ homebrew radio

SWR meter for 1 to 1300 MHz - A very simple design, cheap to built, does not require adjustment and works well! Depending on specific components and construction technique used, the upper frequency limit will be somewhere between 150MHz and 5GHz! __ Designed by Manfred Mornhinweg

The ADC-40 - All Discrete Components 40 M transceiver with super-het receiver using no IC 's, just a whole bunch of transistors of various flavors (NPN, PNP, J-FET, MOSFET) __ Designed by Steven Weber, KD1JV

The BC547 80M SSB QRP Transceiver - This is a bit of a retro design, and uses easily obtained parts, no hard to find or expensive IC 's (no IC 's at all) __ Designed by John Price VK3AJG

USB/LSB Carrier Oscillators - The USB/LSB carrier oscillators are fairly conventional, common collector Colpitts oscillators. I used BC548 transistors, not because they are particularly well suited to the job, but because I had a few of them in my junk box. The crystal frequencies are chosen to match the SSB filter in your rig (7.7985/7.8015 MHz in my rig.) __ Designed by EI9GQ homebrew radio

Using an AVR - LED headlamp projects: Tiny13V microcontroller as step up (boost) or step down (buck) voltage converter for driving a white or high power LED. (pdf file) Design equations and source code included. __ Designed by Steven Weber, KD1JV